Anderson Silva throws shoulder during UFC 148 weigh-in (VIDEO)

During Friday's weigh-ins for UFC 148, middleweight champion Anderson Silva threw a shoulder at longtime rival Chael Sonnen, his opponent for Saturday. The move, which connected with Sonnen's face, led to a tense moment where the two had to be separated by UFC president Dana White. Check out what happened here:

The animosity between the two fighters has been building for two years. They fought at UFC 117, and Silva won with a late submission after being dominated for most of the bout. Since then, Sonnen has called himself the true champion, and said he didn't really lose the fight. He was also quite creative in his insults of Silva's home country of Brazil.

During Thursday's press conference, they also had to be separated, as Silva leaned in and whispered something unknown to Sonnen. But was his shoulder check on Friday over the line?

Scuffling at weigh-ins is not an every day occasion in the UFC, but it's not unheard of. Most recently, BJ Penn and Nick Diaz pushed and shoved before their UFC 137 bout. It's part of the gamesmanship that happens before some fights.